Hot melt glue applicator

ABSTRACT

A hot melt glue applicator including a console for housing controls and a tank containing hot melted glue and at least one glue carrying hose connected with an external glue gun. The device includes separate heaters for the tank, the hose and the gun, an improved solenoid pump for the gun, an automatic fluid pressure release device to prevent hose failure due to high expansion rate of the melting glue, and a pneumatic pump for pumping the glue through the glue carrying hoses to the gun in which seals and packings are eliminated.

United States Patent 1 3,554,408

[72] Inventors Viles K. Fremstad. deceased, late of [56] ReferencesCited Pomona, Calif. by, I I UNITED STATES PATENTS 22 Fremstad'2,555,492 6/1951 Kidney 277 7ox P 1] App No 0325 3,221,937 12/1965Kamborian 222/146 [22 Filed Sept. 16. 1968 Primary Examiner-Stanley l-l.Tollberg [4S] Patented Jan. 12, 197 l An0rneyMolinare, Allegretti,Newith & Witcoff [73] Assignee The Aro Corporation Bryan, Ohio acorporation of Delaware ABSTRACT: A hot melt glue applicator including aconsole for housing controls and a tank containing hot melted glue andat least one glue carrying hose connected with an external glue gun. Thedevice includes separate heaters for the tank, the

[54] HOT MELT GLUE APPLICATOR 9 Claims, 9 Drawing Figs.

[52] U.S. Cl 222/109, hose and the gun, an improved solenoid pump forthe gun, an 222/397 automatic fluid pressure release device to preventhose failure [51] Int. Cl B67d 1/16 due to high expansion rate of themelting glue, and a pneu- [50] Field of Search 222/109- matic pump forpumping the glue through the glue carrying 1 l 1, 146, 397; 277/70;l26/284 hoses to the gun in which seals and packings are eliminated.

PATENTED JAN ,1 2 an 3.554.408 1 sum 3 on:

. m6 k 8 M E NEE PATENTEU JAN 1 219?:

SHEET W 4 7 rBc'y 5 4 ma ow! wa HOT MELT GLUE APPLICATOR BACKGROUND OFTHE INVENTION This invention relates to an improved hot melt glueapplicator. Paperboard cartcbs, corrugated cartons, book 'bindings andpaper bags are commonly fabricated by means of glue which holds theseams and the sides of the various cartons or bugs together. Experiencehas shown that it is best to use a glue which exists in the solid stateat room temperatures since such glues provide more permanent and strongbonds for the cardboard or paper seams. To accomplish this hot melt glueapplicator devices have been provided. Such devices normally include aheater tank adapted to receive glue in a solid particulate form, meltthe glue and maintain it at a temperature which is appropriate for use.Nonnally, this temperature is between 250 F. and 450 F. A pump mechanismof some type is normally included to pump the glue from the heated tankthrough a hose to a glue applicator gun. The glue applicator gun is anozzle arrangement adapted to discharge controlled amounts of glue at acontrolled rate.

When operating at elevated temperatures with a viscous material such asglue, numerous problems are encountered. For example, because the meltedglue expands in volume between percent and percent when changing fromthe solid to the liquid state, the glue carrying conduits, pump or gunmay fail or burst unless some pressure release means is provided. Also,because the glue is normally a highly viscous substance, means forcontrolling and dispensing the glue from the applicator gun aredifficult to provide. It is with problems of this sort that the improvedhot meltapplicator of the present invention successfully overcomes.

SUMMARY OF THE INVENTION In a principal aspect the present invention isthe improvement of means for mounting a liquid glue pump above a glueheater tank in a hot melt glue applicator of the type having a melttank, a pump, and at least one glue gun connected with the tank by meansof the hose means. The pump includes drain ports directed into the tankso that the glue leaking from the unsealed pump passes directly backinto the tank. As an additional feature of the invention the glue gunincludes improved solenoid means for dispensing glue in controlledamounts from the gun discharge orifice.

It is thus an object of the present invention to provide an improved hotmelt glue applicator.

It a further object of the present invention to provide a hot melt glueapplicator which substantially eliminates the problems caused byexpansion of glue changing from the solid to the liquid state.

One further object of the invention is to provide an improved glue gunin combination with a hot melt glue applica- I01.

Still another object of the invention is to provide a glue applicatorhaving a pump which does not require seals and packing.

These and other objects, advantagesand features will be set forth ingreater detail in the description which follows.

BRIEF DESCRIPTION OF THE DRAWINGS In the detailed description whichfollows reference will be made to the drawings comprised of thefollowing FIGS.

FIG. 1 is a top plan view of the heater tank and console, attached gluehose and glue gun, the console having its cover removed;

FIG. 2 is a rear elevation of the unit set forth in FIG. 1;

FIG. 3 is a left-hand end view of the unit shown in FIG. 2;

FIG. 4 is a right-hand end view of the unit shown in FIG. 2;

FIG. 5 is an enlarged cutaway top view of the pump for the glueapplicator system;

FIG. 6 is an enlarged cutaway cross-sectional side view of the pumpshown in FIG. 5; v

FIG. 7 is an enlarged cutaway cross-sectional view of the glueapplicator gun of the invention;

DESCRIPTION OF THE PREFERRED EMBODIMENT The following description isdirected to the mechanical components comprising the glue applicator ofthe invention. The electrical circuitry and control arrangement for theheater components is described in a copending application entitled GlueApplicator Heater Circuit by Theodore H. Davey, filed Sept. 17, 1968,Ser. No. 760,164. Thus, the description of the electronic components ofthis glue applicator system will be generally functional except whereone skilled in the art may find difficulty practicing the invention.There, of course,the description will be more specific. However, thedescription of the mechanical components comprising the invention willbe structurally and functionally described to clearly set forth thesubject matter of the invention.

Therefore, referring to FIGS. 1 through 4, there is shown the completeapplicator system. The components of the applicator are mounted on aframe 10. Positioned on the frame 10 and attached thereto by means ofbolts 12 is a heater tank 14. The tank 14 is surrounded by insulatingmaterials 16. Heater units 18 surround the tank 14 to provide heat formelting solid particulate glue material placed in the tank 14. A screen20 is placed in a receiving receptacle at the bottom of the tank 14 inthe path of a central melt discharge opening 22 at the bottom of thetank 14. Screen 20 serves to filter out materials which are foreign orunmelted before they pass into the pump assembly (described later).Various sizes of screen 20 may be utilized depending upon the glue beingused, etc. The filter screen 20 may be removed by rotating or unscrewingthe attached filter assembly handle 24 and lifting the screen from thetank 14.

Glue which has been melted in tank 14 passes through the opening 22 inthe bottom of the tank 14, into a conduit 26 and finally into the pumpassembly generally shown at 28. The

pump assembly 28 is also maintained at a constant and controlledtemperature by means of a heater element 30 posi tioned longitudinallyalong the assembly 28. Pump assembly 28 is driven by air motor 32. Theliquified glue is pumped from the tank 14 through pump assembly 28 andinto discharge glue hoses as at 34 and 36. An air supply conduit 40providesair to drive the air motor 32. A fluid pressure release cylinder38 pump assembly 28 to provide a glue bypass for relief of pressure dueto the expansion of the glue when changing from the solid to liquidstate, or when cooling after the device is turned off. The air motor andrelief cylinder controls and operation is more fully described below inrelation to FIGIS and FIG. 8.

Control conduits as at 42 and 44 connect with separate glue applicatorguns. Thus, glue hose 34 and control conduit 42 both connect with thesame glue applicator guni In the device illustrated, provision is madefor the inclusion of four glue hoses and their corresponding controlconduits and gun'sfa I hose being connectable to nipple outlets410,411), 41c and 41d. Lead wires 43 from the heater and sensingelements for the tank 14, the control conduit lead wires as at 42, andlead wires as at 45 from the hose as at 34 all connectwith'the-electronic control components positioned beneath the air motor32. Power for heatingthe hoses and the separate glue guns is provided toeach separate hose and glue gunywh'ereas, control leads are providedonly to one hose 34'and'its corresponding glue gun. It has beendetermined that sensing the temperature in one of the hoses and aconnected gun is sufficient to control the temperature of all of thehoses and guns in the applicator since the characteristics of each hoseand gun are'all substantially identical. For this reasonas illustratedin FIG. 1 the hose 34 and control conduit 42 include extra leadwiresforthe control circuitry. The control circuitry provides constanttemcooperates with the perature readings and temperature settings in thetank 14, hose as at 34 and gun. Resistance heaters are used in eachcase.

Referring now to FIGS. 4 and 5 there is shown in greater detail the gluepump assembly 28. The pump assembly 28 is, of course, driven by the rciprocating type air motor 32. The pump assembly 28 includes a housing46 which defines the cylinder of the glue pump. A piston rod 48 isconnected by means of a coupling 50 to a reciprocating drive rod 52 ofthe air motor 32. The rod 48 rides in a bushing 54 threadably secured atone end of the housing 46. No seals are provided between the bushing andthe rod since the pump assembly 28 is positioned over the tank 14 and apair of drain ports 78 and 80 are provided which allow leakage of glueto flow back into the tank 14.

Attached to the end of the piston rod 48 is a valve stem 56. The valvestem 56 rides freely within a slidable piston sleeve 58 and sealsagainst the sleeve 58 during the pressure stroke of the pump. A ballcheck valve 60 which leads from the conduit 26 and tank 14 is providedat the entrance to the cylinder of the housing 46. A second ball checkvalve 62 is positioned in an outlet opening 64 of the housing 46.Opening 64 leads to the nipple connections 41ad for the glue hoses.

Thus, as the piston rod 48 is drawn back into the air motor 32 causingthe valve stem 56 to seat against the piston sleeve 58, glue is drawninto the chamber of the housing 46 and also forced through the secondvalve 62 and outlet 64 and ultimately into the hose 34 which isconnected to the fitting 410. On the return stroke the piston sleeve 58rides back on the valve stem 56 permitting the glue to flow throughopenings in the piston sleeve and into the region traversed by thepiston valve sleeve 58 as it moves forward.

A relief cylinder assembly 68 is attached to the pump assembly 28 andincludes a piston rod 70 which is biased by means of air pressurethrough conduit 72 acting on piston 74. This piston is normally biasedwhen the pump is being operated so that the piston rod 70 operates toclose a bypass passageway 76. When the glue applicator is turned off,however, the air pressure acting on piston 74 is eliminated due tothree-way poppet valve 75 in H6. 8 which vents to the atmosphere. Thispermits the bypass passageway 76 to open and allowing expansion andcontraction of the glue. The relief valve assembly 68 isthermostatically controlled by a thermoswitch 77 so that during heatingof the glue when the glue expands, the relief valve assembly remainsopen to permit the glue in the hoses and pump to expand withoutrupturing the hoses.

Referring now to FIG. 6 there is shown the means by which glue leakingfrom the pump assembly. 28 passes through the pair of drain ports 78 and80 back into the tank 14. The amount of leakage is controlled by sizingthe bushing 54 and piston rod 46. This allows some recirculation of theglue and eliminates a drip pan. A wall 82 defined in the housing 46insures that excess leakage unable to drain down the port 78 will beretained in a pool defined by the wall 82 and will eventually drain downthe drain port 78.

Referring now to FIG. 7 there is shown a typical glue hose and coilconnected to a glue gun of the present invention. In particular a hose34' connects with a fitting on a gun base 86. The hose consists of atetrafluora ethylene tube covered by a stainless steel wire braid. Atape type heating element is wrapped around the wire braid and iscovered by insulation. The entire assembly of the hose is enclosed in afiber glass cloth tube.

The gun base 86 forms the framework upon which the gun assembly isconstructed. Fluid glue passes through the hose 34 and through thedischarge end of the gun base 86 into a nose piece 88. A cap 90 isattached to the nose piece 88 and holds a tip 92 in secure communicationwith the nose piece 88.

Positioned inside the gun base 86 is a spring biased plunger 94. Plunger94 is biased by spring 96 so that the tip end 98 of the plunger 94engages an orifice ofan inner nose piece 100 which provides a path forfluid glue between the interior gun base and the orifice through the tip92.

An electromagnetic coil 102 is positioned about the gun base 86. Uponactivation of the coil 102 through coil leads 104. the plunger 94 iscaused to rise permitting a flow of glue along the sides of the plunger,into thetip 92 and out of the the plunger 94.

The outer circumference of the plunger includes four shallow flatportions 111 through 114 as illustrated in FIG. 70. On the lower shankportion of the plunger 90 at the outside diameter, shank flat portions116 and l 17 are defined. This arrangement allows the fluid glue to flowdown the sides of the plunger 94 and also makes four regions'in whichthe volume between the plunger 94 and inside diameter of the gun base 86is greater thus avoiding excessive fluid'friction drag. Shank flats 116and 117 also provide a region between the nose piece 88 and the lowerpart of the shank of the plunger 94 so that glue may easily flow fromthe tip 92. With a construction of this type the valve can be cycled atvery high rates because of the low viscous drag. Rates up to 25,000cycles per minute are thereby possible.

The upper end of the plunger 90 which engages the gun base 86 is alsospecially constructed. The upper end includes a narrow circular seat 91having a reduced contact area between the plunger 90 and gun base 86.This has the advantage of providing a vacuum type breaking action whenthe electrical signal is removed from the coil 102. Thus, the spring 96will quickly and firmly drive the plunger 94 to close the orifice of thetip 92.

A removable cover or housing 120 having an arm extended coil connectionportion 122 is also provided for the gun; The arm portion 122 includes acover 123 which may be removed to expose the connections between thevarious leads to the gun. Moreover, the housing 120 and arm 122 may beentirely removed and interchanged with another housing and arm, theother arm being repositioned in relation with the housing foralternative modes of clamping the gun in relation to an as sembly lineor another package making machine. Such an alternative mode isillustrated in phantom in FIG. 7.

An advantage of the gun construction described results from the factthat the fitting 85 is positioned at a 45 angle to the top of thehousing 120 and coil 102. Thus, the hose may be easily attached in themanner illustrated in H6. 7. In addition, as illustrated by the phantomlines in FIG. 7 the gun base may be rotated and an alternative housing120 and attached arm 122 may be used in cooperation with the hose 84 andthe remaining components of the gun without breaking any fittings orconnections in the glue passage line.

Within the arm 122 is a sensor lead 124 connected with a temperaturesensor 126. Heater leads 128 connect to a circumferential heater element130 positioned on the gun base 86. A shield 132 protects the heater 130and also serves to keep heat contained within the shields 132. Theseleads connect with connectors in the conduit which leads back to thecontrol circuitry described before.

FIG. 8 illustrates the pneumatic air diagram for the unit. Fil tered,lubricated and pressure regulated air enters through supply conduit 40and into poppet valve 75. F rom a T connector 136 a conduit 138 connectswith the relief cylinder assembly 68. Another conduit 140 connectsthrough regulator 142 to the air motor 32. A gauge 144 provides constantmonitoring for the air pressure to the motor 32.

It is claimed:

1. In a hot melt glue applicator device of the type having a melt tankfor holding andmelting glue, a pump for pumping said glue from saidtank, at least one glue gun for dispensing said melted glue, hose meansconnecting said tank with said gun, and temperature and pressure controlmeans for controlling the temperature of said melted glueand the rate ofdischarge of said glue from said gun, the improvement comprising, incombination; means for mounting said pump above said tank, said pumpincluding drain ports directed into said tank such that glue in sai.pump passes directly into said tank when leaking from said pump.

2. The device as set forth in claim 1 wherein said pump is areciprocating piston type pump including a cylinder, a valve connectionwith said tank, a valve connection to said hose means, said piston beingdriven by a piston rod connected with an external motor, a bushing beingprovided for said piston rod in said pump, the clearance between thepiston rod and the bushing allowing leakage through said bushing andsaid drain port directly back into said tank.

3. The hot melt glue applicator device of claim 1 including releasecylinder means as adapted to bypass said valve connections positionedintermittent said pump and said hose means, said release cylinder meansincluding means for automatically actuating when said applicator deviceis not being operated to relieve expansion and contraction of said meltwhen being heated or cooled respectively.

4. The device as set forth in claim 3 wherein said control meansincludes thermostatic control means for said release cylinder meansoperable to maintain said release cylinder means in an open positionwhile said glue is being heated thereby to compensate for expansionofsaid glue changing from a solid to a liquid state.

5. The improvement as set forth in claim 1 wherein said glue gunincludes a solenoid with a plunger having at least one flat side on itsoutside diameter to allow 'fluid to flow down the side of said plungerand out an orifice of said gun disposed axially of said plunger, saidplunger operative in response to said solenoid to alternately open andclose said orifice thereby discharging said glue through said orifice.

6. ln a hot melt glue applicator system of the type having a melt tankfor holding and melting glue, a pump for pumping said glue from saidtank, at least one glue gun for dispensing said melted glue, hose meansconnecting said tank to said gun, and temperature and pressure controlmeans for controlling the temperature of said melted glue and the rateof discharge of said glue from said gun, the improvement comprising incombination; a glue gun including a solenoid with a plunger, saidplunger having at least one flat side on its outside diameter to allowfluid to flow down the side of said plunger and out an orifice of saidgun disposed axially of said plunger. said plunger operative in responseto said solenoid to altemately open and close said orifice therebydischarging said glue from said orifice.

7. The improvement as set forth in claim 6 wherein said plunger has fourshallow flats on its outside diameter for allowing fluid glue to flowthereby avoiding excess viscous drag.

8. The improvement as set forth in claim 6 wherein said gun includes aremovable cover adapted to enclose said temperature and pressure controlmeans on said gun and which also provides a clamping surface to mountsaid gun.

9. The improved device as set forth in claim 6 wherein said conduit isconnected with said gun by means of a fitting interconnected with saidhose means.

1. In a hot melt glue applicator device of the type having a melt tankfor holding and melting glue, a pump for pumping said glue from saidtank, at least one glue gun for dispensing said melted glue, hose meansconnecting said tank with said gun, and temperature and pressure controlmeans for controlling the temperature of said melted glue and the rateof discharge of said glue from said gun, the improvement comprising, incombination; means for mounting said pump above said tank, said pumpincluding drain ports directed into said tank such that glue in saidpump passes directly into said tank when leaking from said pump.
 2. Thedevice as set forth in claim 1 wherein said pump is a reciprocatingpiston type pump including a cylinder, a valve connection with saidtank, a valve connection to said hose means, said piston being driven bya piston rod connected with an external motor, a bushing being providedfor said piston rod in said pump, the clearance between the piston rodand the bushing allowing leakage through said bushing and said drainport directly back into said tank.
 3. The hot melt glue applicatordevice of claim 1 including release cylinder means as adapted to bypasssaid valve connections positioned intermittent said pump and said hosemeans, said release cylinder means including means for automaticallyactuating when said applicator device is not being operated to relieveexpansion and contraction of said melt when being heated or cooledrespectively.
 4. The device as set forth in claim 3 wherein said controlmeans includes thermostatic control means for said release cylindermeans operable to maintain said release cylinder means in an openposition while said glue is being heated thereby to compensate forexpansion of said glue changing from a solid to a liquid state.
 5. Theimprovement as set forth in claim 1 wherein said glue gun includes asolenoid with a plunger having at least one flat side on its outsidediameter to allow fluid to flow down the side of said plunger and out anorifice of said gun disposed axially of said plunger, said plungeroperative in response to said solenoid to alternately open and closesaid orifice thereby discharging said glue through said orifice.
 6. In ahot melt glue applicator system of the type having a melt tank forholding and melting glue, a pump for pumping said glue from said tank,at least one glue gun for dispensing said melted glue, hose meansconnecting said tank to said gun, and temperature and pressure controlmeans for controlling the temperature of said melted glue and the rateof discharge of said glue from said gun, the improvement comprising incombination; a glue gun including a solenoid with a plunger, saidplunger having at least one flat sIde on its outside diameter to allowfluid to flow down the side of said plunger and out an orifice of saidgun disposed axially of said plunger, said plunger operative in responseto said solenoid to alternately open and close said orifice therebydischarging said glue from said orifice.
 7. The improvement as set forthin claim 6 wherein said plunger has four shallow flats on its outsidediameter for allowing fluid glue to flow thereby avoiding excess viscousdrag.
 8. The improvement as set forth in claim 6 wherein said gunincludes a removable cover adapted to enclose said temperature andpressure control means on said gun and which also provides a clampingsurface to mount said gun.
 9. The improved device as set forth in claim6 wherein said conduit is connected with said gun by means of a 45*fitting interconnected with said hose means.